Alzheimer's disease, already a serious global disease afflicting large segments of the population, is about to burgeon into an even larger problem as the baby-boomer bubble approaches retirement age. The disease remains incurable;however validated therapeutic targets are known. RNA interference (RNAi) technology poses a potential therapeutic option which requires further investigation. Targeting the mRNA rather than the protein offers major advantages in the ease of designing a highly specific inhibitory agent and rapidly advancing approaches to RNAi delivery suggest that the method can be developed into a therapy. Our hypothesis is that RNAi will prove to be an effective and selective strategy to slow, and perhaps even reverse, the pathogenic processes in inherited and sporadic AD. This proposal follows the completion of an R21 award of the same title. The announcement for this award was an RFA from the Fogarty Institute for proposals related to Brain Disorders in the Developing World and a major goal of the program was to build research capacity at the foreign site. The successful completion of the R21 aims is described in the preliminary data. The collaborative effort poses two questions concerning the cause and possible treatment of neurofibrillary pathology in AD. One question is whether suppression of Cdk5, an increasingly accepted disease target, can modify neurofibrillary pathology in an animal model. Cdk5 is an enzyme that phosphorylates tau protein and in so doing is thought to contribute to the conversion of the protein into an insoluble aggregate known as the neurofibrillary tangle. Cdk5 will be targeted by RNAi delivered in a viral vector. The second question is whether BACE1 inhibition by RNAi delivery can retard or prevent the development of neurofibrillary pathology in an animal with both plaques and tangles. The studies proposed here are intended to continue building research capacity at the foreign site which is now in a position to launch these studies. In addition to the established collaboration between the Kosik laboratory and the foreign site, two consultants will contribute to capacity building. They are Bev Davidson who will advise on the establishment of a viral core and Frank LaFerla who will contribute the triple transgenic mice to the vivarium at the foreign site.